Light deflecting mechanisms



v March 25, i969 w. L.. DUDA ET AL LIGHT DEFLECTING MECHANISMS SheeJclFiled March l, 1965 INVENTORS WILLIAM L DUDA HAROLD FLEiSHER WERNER W.KULCKE ERHARD MAX- BY 'f" ATTORNEY March 25, 1969 w, 1 DUDA ET A1.3,435,447

I LIGHT DEFLECTING MECHANISMS Filed March l, 1965 Sheet Z of 2 FIG.3

United States Patent C) U.S. Cl. 340-347 8 Claims ABSTRACT F THEDISCLOSURE Light deiiecting apparatus including control circuits forlight deflectors which perform the Exclusive-OR logical function on agiven stage of the deflector and the next succeeding stage in activatingthe polarization rotators of the deflector. Thus, if the controlcircuits are energized at locations representative of different Values,light deflection takes place through the deflector to positionsrepresentative of the sum of the values.

This invention relates to light deectors, and more parn ticularly tolight deectors having control circuits which may be energized by pulsesapplied at points representative of different values to eifect adeilection of light to positions representative of the sum of thevalues.

There is described in a patent application, Ser. No. 285,832, led lune5, 1963 by T. l. Harris et al., a light deector including birefringentcrystals through which a linearly polarized light beam passes over oneor another of two paths depending on the directionl in which the lightbeam is polarized. At the input side of each crystal is an electro-opticdevice which normally passes linearly polarized light without changingits direction of polarization. Under these conditions the light may bepolarized in such a plane that it passes through the associatedbirefringent crystal as an ordinary ray. When a half Wave Voltage isapplied, however, to the electro-optic device, the plane of polarizationis rotated 90 degrees and the light beam passes through the birefringentcrystal as an extraordinary ray. The ordinary and extraordinary raysleave the crystal at points spaced laterally of each other distanceswhich are directly proportional to the thickness of the crystal. Byproviding a deflector having several birefringent crystals, each havinga thickness proportional to some assigned num meric value and alsohaving an electro-optic device at its input si'de, it is possible toobtain a deection of a light beam to any position representative of thesum of the values assigned to crystals which were made effective by theenergizing of electro-optic devices.

In the application mentioned above, each electro-optic device in amulti-stage deilector is energized and de-energized independently of theother electro-optic devices by the closing and opening of a switch. Ifthe light beam entering any selected stage is polarized in a ldirectionto pass through its crystal as an ordinary ray and it is desired thatdeflection take place in such stage, then the switch for theelectro-optic device at the stage input must be closed. The switch forthe electro-optic device of the following stage must also be closed ifthe light deflection is to 'be limited to the selected stage, otherwisethe light will remain polarized in a direction to be Ideflectedz'in eachstage through which is passes.

It has been discovered that control circuits may be pro- \ided -forenergizing the electro-optic devices of a multi- :tage deector in such amanner that the outputof the last stage is always located at a -pointrepresentative of the sum of the numeric values of ydifferent stages towhich 3,435,447 Patented Mar. 25, 1969 input pulses are delivered. Thedeection values of the different stages may either be the same ordifferent depending on the manner in which the deflector is to be used.By making each stage of a deflector equal in deflection value, there isobtained an output located at a position representative of the sum ofthe ones in a binary number appliedto the deector. When the vthicknessof the birefringent crystals vary according to different nu-i mericvalues, the position of the output for the deflector is proportional tothe sum of the values assigned to crystals having electro-optic deviceswhich were pulsed. By serially pulsing 4positions increasing in value byone, a scanning action is obtained at the output. The thickness of thebi= refringent crystals may be varied in a manner to give an independentdiscrete output position for all possible com- |binations of switchclosings. The preferred thickness variation in such case is one in whicheach crystal exceeds the thickness of the preceding crystal by a factorof two. By providing each stage of a deector with two crystals of thesame thickness, each having its own electro-optic device, and increasingthe thickness of the crystals from one stage to the next by a factor oftwo, it is possible to ener= gize the electro-optic devices for the twosets of crystals according to different binary numbers and obtain anoutput representative of the sum of the two numbers. Regardless of thethickness of the crystals employed in each detiector, the electro-opticdevices are energized through exclusive or circuits in such a mannerthat a pulse -which energizes the electro-optic device of one stage alsoenergizes the electro-optic device for the next succeeding stage unlessanother pulse is also delivered to that stage. Also, a pulse deliveredto any stage is effective to energize its electrooptic -device only whenthere has been no pulse delivered to the next preceding stage.

An object of this invention is to provide a light defiector havingelectro-optic devices which are energized by improved control circuits.

Another object is to provide a light dellcctor having a plurality ofstages to which electric pulses may be delivered for eifecting lightdeflection, and the position of the light output for the last stagebeing representative of the sum of the stages to which pulses aredelivered.

Still another object is to provide a lmulti-stagev light deiiector towhich pulses may be applied successively vfor providing a scanningaction of the light at the output.

Yet another object is to provide an improved light deflector havingelectro-optic devices which may be energized by pulses representative ofdifferent binary numbers and produce an output at a positionrepresentative of the sum of the two numbers.

The foregoing and other objects, features and advantages of the presentinvention will be apparent from the following more particulardescription of the preferred embodiments of the invention as illustratedinthe accompanying drawings.

In the drawings:

FIG. 1 is a schematic diagram of apparatus for detiecting la light beamvertically to a level representative 0f the`sum of values assigned topoints at which pulses are delivered to a control circuit.

I FIG. 2 is a schematic diagram of a system like that of FIG. l buthaving both vertical and horizontal deectors.

FIG. 3 is a schematic diagram of a system similar to FIG. 1 but havingequal values assigned to the different deflector stages.

FIG. 4 is a diagram of a light deilector having different stagesarranged in a manner to produce a light output at points representativeof the sum of two binary numbers.

Referring to the drawings, and more particularly to FIG. 1, it will benoted that there is shown a multi-stage light deflector capable ofdeecting a beam 2 of linearly polarized light vertically to positionsrepresentative of the sum of the deflection values for the stages whichare made effective by a closing of switches. There are provided, asshown, light deflection stages 4, 6, 8, X which are operable to deflectlight vertically distances increasing by a factor of two. The deflectionstages include birefringent elements 10, 12, 14 and 16X which may becrystals cut specially to allow incoming plane polarized light to passthrough them in one path or another as either an ordinary ray or anextraordinary ray but not both simultaneously. The path followed dependsupon the direction in which the beam entering the crystal is polarized.A beam plane polarized perpendicular to the plane of the drawing willpass, for example, through the crystal without deflection as theordinary ray. If the light is polarized parallel to the plane of thedrawing, it will be deflected and pass as the extraordinary ray over adifferent path. The spacing between the points at which the ordinary andextraordinary rays leave the crystal is directly proportional to thethickness of the crystal. To provide deflection stages increasing by afactor of two, the thickness of the crystals used in these stages mustincrease by the same factor.

At the input sides of the birefringent elements 10, 12, 14 and 16X areelectro-optic devices 18, 20, 22 and 24X. Each of these devices is madeup of an electro-optic crystal 26 between a pair of transparentelectrodes 28. When a potential of sufficient magnitude is appliedacross any one of the electro-optic devices, a rotation of the plane ofpolarization `of the light by 90 degrees takes place. For applying sucha potential selectively across these devices, one electrode of eachdevice is connected to ground while the other electrodes are connectedthrough switches 30, 32, 34 and 36X to one side of a potential -source38 which is connected at its other side to ground. The electro-opticdevices for all stages except the first are connected to theirrespective switches through exclusive-or circuits 40, 42 and 44X, andare also connected through their exclusiveor circuits and conductors 46,48 and 50X to the switches for the next preceding stage. Theelectro-optic device for the first stage is connected directly to itsswitch 30 through a conductor 52, Mechanical switches are shown hereinonly to provide an understanding of the invention. In actual practice,electronic switching means responsive to coded electric pulses would beused. The potential at the source 38 is of sufiicient magnitude toeffect a rotation of the plane of polarization of the light beam by 90degrees as it passes through any one of the electro-optic devices havinga potential applied across it by the closing of a switch.

The beam of light 2 is supplied from a suitable source, such as a laser53, through a collimating lens 54 and a polarizer 56 to theelectro-optic device 18 of the first stage polarized in a planeperpendicular to the plane of the drawing. If all of the switches wereopen, the light beam would pass through the birefringent elementswithout deflection as the ordinary ray. With the switch 30 closed, asshown, the electro-optic device 18 is energized to effect a rotation ofthe plane of polarization by 90 degrees so the light beam is deflectedin crystal 10. The closing of switch 30 also applies a voltage throughconductor 46 to the exclusive-or circuit 40. With switch 32 open, avoltage is applied through circuit 40 to the electro-optic device 20 foreffecting a rotation of the plane of polarization 90 degrees to itsoriginal plane. lf the switch 32 had been closed there would be novoltage applied from the exclusive-or circuit 40 to the electro-opticdevice 20 and the polarization of the light would have remained in theplane to which it was rotated by the device 18. The light beam wouldthen be deflected in crystal 12 the same as it was in crystal 10. Withswitch 32 open, however, the light beam passes through crystal 12without deflection. Switch 34 being closed while switch 32 is openresults in the energizing of the electro-optic device 22 to rotate theplane of polarization 90 degrees and effect a deliection of the lightbeam in crystal 14- The exclusive-or circuit at the next higher stage isconditioned, if the switch at that stage is open, to energize the nextelectro-optic device and rotate the plane of polarization again 90degrees. Assuming that the switches 30, 32, 34, 36X are assigned valuescorresponding to the values of the birefringent elements 10, 12, 14, 16Xwith which they are associated, then the total value of the lightdeflection is equal to the total of the values assigned to the switcheswhich are closed. With the switches 30 and 34 closed, as shown, thetotal of the light defiection obtained is ve units since crystal 10produces a deliection of one unit while crystal 14 produces a deflectionyof four units. It will be appreciated that the output of light from thefinal stage may `be at any value from zero to the sum of the valuesassigned to the switches at all of the stages.

There is shown in FIG. 2 a light deliector in which the first threestages 60, 6.1 and 62 are like those of FIG. 1 and deflect the light-beam vertically in response to the closing of switches 63, `64 and 65.The next three stages 66, 67 and 68 have birefringent elements 69, 70and 71 turned 90 degrees relative to the birefringent elements of thefirst three stages so that deflection of light in these stages takesplace in a horizontal direction. At the input sides of the elements 69,70 and 71 are electro-optic devices 74, 75 and 76 like those of thefirst three stages. The thickness of the elements 69, 70 and 71increases by a factor of two from right to left as it does for thebirefringent element of the first three stages. It is possible to obtainwith this arrangement an output of light from element 71 at any one ofpoints 0 to 7 spaced vertically in any one of columns 0 to 7 spacedhorizontally. A closq ing of switches 63, 64 and 65 alone or incombination re= sults in an output of light from element 71 at one ofthe points 0 to 7 in a vertical plane including the light beam 2. Sincelight passing through the birefringent elements of the first threestages as either an ordinary or extra ordinary ray would pass throughthe elements 69, 70 and 71 as the opposite type of ray due to theirchange in angular positions by 90 degrees, it is necessary that a halfwave plate 78 lbe located between the output of stage 62 and theelectro-optic device 74 for the first horizontal detlecting stage. Theelectro-optic devices 74, 75 and ,'76 are energized through exclusive-orcircuits 79, 80 and 81 and switches 82, 83 and 84 in the same manner asthe electro-optic devices for the stages 61 and 62.

When all of the switches are open, the light beam passes through thefirst three stages polarized in a plane perpendicular to the plane ofthe drawing and no deflection takes place. The plane of polarization isthen rotated degrees by the half wave plate 78 and passes through thenext three stages polarized in a plane parallel to the plane of thedrawing. Still no deflection takes place due to the orientation of thebirefringent elements 69, 70, 71 and light leaves the last element nearits lower front corner.

If the switches 63, 64 and 65 were closed, the light beam would bedeflected upwardly in each of the first three stages. It would pass fromstage 62 through the half wave plate 78 so it would be conditioned fordeflection in the next three stages. The closing of switch 65, however,would energize the electro-optic device 74 so the plane of polarizationwould be rotated again to a plane in which the light beam passes throughthe last three stages without defiection. Light output from element 71would then be located at the uppermost point in the forward plane. Aclosing of switches 82, 83 and 84 alone or in combination would cause adeflection of the light beam from one to seven units horizontallydepending on the values assigned to the elements whose associatedswitches were closed.

There is shown in FIG. 3 a system like that of FIG. l except that eachof the birefringent elements 86, 87, 88 and 89X is of the same thicknessand has assigned to it a value of one. Electro-optic devices 18, 20, 22and 24X at the input sides of the birefringent elements are energizedthrough circuitry including exclusive-or cirmay cuits 40, 42, 44X andswitches 30, 32, 34 and 36X the same as in FIG. 1. With thisarrangement, the output point of the light beam from the last deflectionstage is representative of the number of ones in a binary numberassuming that the switches at positions corresponding to the binary onesare closed while those at positions corresponding to binary zeros areleft Open. With the switches 3032 and 36X closed as shown, the outputlight appears at position three indicating that a binary number havingthree ones was applied to the system.

lngfFlG. 4 there is shown an arrangement of light deection stages inwhich the output position of the light at the last stage isrepresentative of the sum of two binary numbers. The arrangementconsists 0f two sets of deflectioiif, elements, each set includingbirefringent elements increasing in thickness by a factor of two. Oneset of elemehts, numbered 91a, 92a and 93a, is interspersed withthe;.other set numbered 91b, 92b and 93b. Switches 94a, 95a and 96acontrolthe energizing of electro-optic devices 97a, 98a and 99a for thefirst set of elements while switches 97b, 98b and 99b control theenergizing of electro-ptic devices for the second set. As shown in FIG.4, switches 95a and 96a of the first set are closed while switch 94afis`open. These positions of the switches represent the birar'y number 1/10.Only switches 94b and 95b of the sec'nd set are closed as arepresentation of the binary number 011. Adding the two ybinary numbersgives 1001 which is equal to the decimal number 9, and it will be notedfrom the drawing that the energizing of the electro-op- 'ticidevicesthrough the exclusive or circuits effects a deection of the light beamin elements 91b, 92a, 92h and 93a for a total number of nine units. Itwill =be appreciated that the birefringent elements of the two sets neednot be interspersed as shown but could be arranged with one setfollowing the other or in any other arrangement desired. It is onlynecessary that the switches for each set be operated to control thedeecton of light in birefringent elements at positions corresponding tothose in the binary numbers for which the switches wereoperated.

In each of the systems shown there may be provided, if desired, at eachoutput position of the `final .deflection stage a light responsivedevice which either provides an indication When light is directed uponit from the deflector or effects some operation in accordance with thedeflection obtained.

While thev invention has been particularly shown and describedwitlitreference to preferred` embodiments thereof, it will be understoodby those skilled in the art that the foregoing and other changes in formand details may be made therein without departing from the spirit andscope of the invention.

What is claimed is: .1. Light deiiecting apparatus comprising, incombinafg, plurality 'of light deecting stages through which a beam oflinearly polarized light may be passed either with or without deflectiondepending on its plane of polarization,

means for directing through` said stages a -beam of light polarized in aplane to pass normally therethrough without deflection,

an electro-optic device at the input side of each deflecting stageoperable when energized to rotate the plane "of polarization by 90degrees,

a switch associated with each electro-optic device, and

means coupling each electro-optic device except the r'st electro-opticdevice to its associated switch and to the switch of the next precedingstage, the first electro-optic device being directly coupled to itsassociated switch, so that an electro-optic device is energized when theswitch associated with such device is closed if the switch for the nextpreceding stage is open and so that the next succeeding electro-opticdevice is also energized when the switch associated with that succeedingstage is open.

2. The light deflecting apparatus of claim 1 in which said lastmentioned means includes an exclusive-or circuit connected to eachelectro-optic device except for the rst stage,

and means for energizing each exclusive-or circuit from either or bothof the switches of the associated stage and the next preceding stage.

3. The light deflecting apparatus of claim 1 in which each stageincludes a birefringent element which lpasses light eithe'ra-s anordinary r-ay or an extraordinary ray depending on the direction of itsplane of polarization,

andsaid birefringent elements increase in thickness by ',a factor of twofrom one stage to the next whereby the light output at the last stage islocated at a posi` tionrepresentative of the sum of the values in abinary number at locations corresponding to stages made .effective by aclosing of switches.

4. The light deflecting apparatus of claim 1 in which each stageincludes a birefringent element which passes light either withoutdeflection as an ordinary ray or with deection las an extraordinary raydepending on the direction of its plane of polarization,

some of said birefringent elements being oriented to deilect light in agiven plane and others being oriented -todeflect light in a plane atdegrees to said given plane,

and a half wave plate arranged between said birefringent elementsdeflecting light in a plane at 90 degrees relative thereto.

5. The apparatus of claim 4 in which the thickness of said elementsdeflecting light in one plane increases by a factor of two and thethickness of said elements deflecting light in a plane at 90 degreesrelative thereto corresponds to that of the first mentioned elements andincreases inthe same order.

6. Light deflecting apparatus comprising, in com-bination:

a plurality of light deflecting stages,

each of said'stages including la birefringent element of unit thicknessthrough which linearly polarized light may be passed either withoutdeflection as an ordinary ray or with deection as an-extraordinary raydepending on the plane of polarization,

an electro-optic device at the input side of each :birefringent elementoperable when energized for rotating the plane of polarization by 90degrees,

a switch associated with each electro-optic device and representative ofa binary one when closed and a binary zero when open,

an exclusive-or circuit connected |between each electro-optic device andits associated switch as well as the switch of the next preceding stage,

and means for directing through said stages a ybeam of light polarizedin a plane to pass normally therethrough as an ordinary ray,

said light beam being deflected in birefringent elements followingelectro-optic devices 'Whose associated switches are closed so the lightoutput at the last stage is lat a position representative of the sum ofones in a binary number represented by positions of said switches.

7.l Apparatus for deflecting a light Ibeam to positions representativeof the sum of two binary numbers comprising, in combination:

two sets of light dellection stages arranged in alignment so that aibeam of light passes through them serially,

the light deflection stages of each set including birefringent element-sincreasing in thickness by a factor of two,

an electro-optic device at the input side of each birefringent element,

means including a switch associated with each electrooptic device andoperable when closed for energizing its lassociated device if the switchfor the next preceding stage is open, each switch also effecting anenergizing or' the electro-optic device for the next succeeding stage ifthe switch for the latter stage is open,

each of said switches `being representative of a'binary one when closedand a binary zero when open,

and means for directing through said stages a beam of light polarized ina plane to pass normally therethrough as an ordinary ray,

said lght beam being deflected in birefringent elements followingelectro-optic devices whose associated switches are closed so the lightoutput at the last stage is at a position representative of the sum oftwo |binary numbers, each corresponding to positions of a different setof switches.

8. The apparatus of claim 5 in which said means for energizing saidelectro-optic devices includes exclusiveor circuits, each connectedbetween an electro-optic device and its associated switch as Well as theswitch for the next preceding stage.

References Cited UNITED STATES PATENTS OTHER REFERENCES W. V., Smith:Electro-Optic Deflection Device, IBM

Technical Disclosure, vol. 6, Nor12, May 1964.

10 MAYNARD R. WILBUR, Primary Examiner.

.TEREMIAH GLASSMAN, Assistant Examiner.

U.S. Cl. XR.

